共查询到20条相似文献，搜索用时 31 毫秒
1.
Growth chamber experiments were conducted in order to study the absorption, translocation and activity of glyphosate when applied to roots with aqueous solution avoiding any glyphosate–substrate interaction. Corn seedlings at the first leaf stage were set up in individual graduated cylinders containing different solutions of 14 C-glyphosate (0–30 mg ae kg−1 ). After 26 h of root exposure, plants were transferred to fresh nutrient solution and grown for the next 5 days. After harvest, plants were separated into seed, root, mesocotyle, coleoptile, cotyledon, first leaf and all new leaves (apex), and quantified 14 C radioactivity contained in each part. Glyphosate uptake was only 11% of the theoretical mass flow into the plant. The amount of glyphosate translocated from roots was positively correlated with plant uptake ( P < 0.01). Total plant fresh weight presented a logistic response to glyphosate amounts, including a growth stimulant effect (hormesis), when plants absorbed less than 0.6 µg. The treated plants presented a normal pattern of glyphosate allocation, with the apex the principal sink, accumulating more than 38% of mobilized glyphosate. When corn plants absorbed more than 0.6 µg they showed a decrease in growth. The relatively high glyphosate quantities allocated in the new leaves showed the relevance of the symplastic pathway in the translocation process for root absorbed glyphosate. 相似文献
2.
In this study, we evaluated the release of diclofop-methyl and triasulfuron from the roots of foliar-treated ryegrass and wheat. The study with 14 C-diclofop-methyl indicated a basipetal translocation of foliar-applied herbicide in wheat and ryegrass. No root exudation from 14 C-diclofop-methyl-treated wheat plants was observed, while 20 days after treatment (DAT) 0.2–0.9% of radioactivity absorbed by ryegrass was found exuded in the growing medium. Root exudation was stimulated three to six times by the presence of untreated wheat or ryegrass sharing the growing medium with diclofop-methyl-treated ryegrass. No subsequent uptake of exuded radiolabel by untreated plants (ryegrass or wheat) in the same pot with 14 C-diclofop-methyl-treated ryegrass was observed. The study with 14 C-triasulfuron indicated a basipetal translocation of foliar-applied herbicide in wheat and ryegrass and also into the growing medium. By 20 DAT, 0.5–4.2% of radioactivity absorbed by wheat or ryegrass was found exuded in the growing medium. The presence of untreated plants (wheat or ryegrass) in the same pot as triasulfuron-treated ryegrass or wheat induced exudation seven to 32 times more. The study also revealed a subsequent uptake of exuded compounds by untreated wheat or ryegrass sharing the medium of 14 C-triasulfuron-treated plants. This study has demonstrated for the first time that the root exudation of exogenous compounds can be related to plant arrangement in pots. The implication is that herbicide root exudation and transfer, a form of allelopathy, could be significant in the field. A precise estimation of environmental fate, unexpected ecological side effects and residual activity of herbicides may require quantification of such exudation. 相似文献
3.
The take-all fungus, Gaeumannomyces graminis var. tritici , was highly sensitive to fluquinconazole ( in-vitro EC50 0·016–0·018 mg L−1 ), a fungicide developed for use as a seed treatment to control take-all, and to prochloraz (EC50 0·006 mg L−1 ). Fungi of other genera that were commonly isolated from cereal roots were sensitive in varying degrees to prochloraz but were relatively insensitive (e.g. Fusarium culmorum , EC50 > 20 mg L−1 ) or slightly sensitive (e.g. Epicoccum purpurascens , EC50 0·514 mg L−1 ) to fluquinconazole. Gaeumannomyces graminis var. graminis and G. cylindrosporus , weak parasites that can protect roots against take-all, and an unnamed Phialophora sp., all closely related to the take-all fungus, were highly or moderately sensitive to fluquinconazole. Alternaria infectoria and E. purpurascens were most consistently effective in suppressing development of take-all on pot-grown wheat plants dual-inoculated with G. graminis var. tritici and the nonpathogen. Take-all was decreased more on dual-inoculated wheat plants grown from seed treated with fluquinconazole or fluquinconazole plus prochloraz than when only an antagonistic fungus ( A. infectoria , E. purpurascens , Fusarium culmorum or Idriella bolleyi ) or a seed treatment was applied. These fungi were less effective in combination with seed treatments on barley. Gaeumannomyces graminis var. graminis and G. cylindrosporus , tested on wheat, suppressed take-all only in the absence of fungicides. It is suggested that the performance of seed treatment containing fluquinconazole against take-all may in some circumstances be enhanced by its partial specificity for the take-all fungus. 相似文献
4.
Rooted cuttings of Pyrus melanocarpa (Michx.) Willd. had a 3.5-fold greater tolerance to soil-applied hexazinone than those of Rubus hispidus L. in a greenhouse trial. R. hispidus accumulated four times more 14 C-label in the foliage following root uptake of 14 C-hexazinone than P. melano-carpa . Here, the greater uptake and susceptibility of R. hispidus was related to its greater root:fol-iage (weight) ratio compared to the tolerant P. melanocarpa . However, in whole plant metabolism studies employing younger plants there were no differences in 14 C accumulation in the leaves. Here 14 Chexazinone was converted to a number of hydroxylated and/or demethylated triazinone metabolites in both species following vacuum infiltration into leaf disks and root sections, or following root uptake in whole plants. A major difference in metabolism between the two species was the greater formation of the mono demethylated metabolite, B, [3-cyclohexyl-6-methylamino-l-methyl-l,3,5-triazine-2,4-dione] in P. melanocarpa which may also contribute to its greater tolerance. A loss of total 14 Clabel from all plant parts with time may reflect cleavage of the 14 C-ring-labelled herbicide. 相似文献
5.
Effects of nitrogen, phosphorus, potassium and calcium nutrition on strawberry anthracnose 总被引：1，自引：0，他引：1
The effects of a range of concentrations of four nutrients – nitrogen, phosphorus, potassium and calcium – in fertilizer solutions on the severity of anthracnose on strawberry cv. Nyoho cultivated under a noncirculation hydroponics system were determined after inoculation with Colletotrichum gloeosporioides . Crop growth and tissue nitrogen, phosphorus, potassium and calcium contents of the entire above-ground parts of the plant were also investigated. Elevated nitrogen and potassium concentrations in the fertilizer solution increased disease severity in contrast to phosphorus and calcium. Treatment with either NH4 or NO3 nitrogen was not significantly different. The dry weight of the strawberry plants increased significantly with elevated concentrations of nitrogen ( R 2 = 0·9078) and phosphorus ( R 2 = 0·8842), but was not influenced by the elevated amounts of potassium ( R 2 = 0·8587) and calcium ( R 2 = 0·6526) concentrations. 相似文献
6.
ANN-MARIE DOCK GUSTAVSSON 《Weed Research》1997,37(4):229-236
The undisturbed growth and regenerative capacity of the root system of Cirsium arvense (L.) Scop, were studied in one glasshouse and one field experiment. In the glasshouse experiment, two lengths of root fragment from the same clone, previously grown at two nitrogen levels, were planted in boxes. Plants that developed from these fragments were inspected on eight occasions to assess their undisturbed development and growth, above and below ground, and their regenerative capacity after disturbance by burial at different points of development. The initial nitrogen content of the roots had no effect on growth measurements, but longer root fragments produced greater masses of primary shoots, new roots and shoots from the new roots than did shorter ones. After disturbance at early stages (4-7 leaves with a minimum length of 5 cm), plants originating from shorter root fragments did not regrow at all. Plants originating from longer root fragments exhibited a minimum regenerative capacity when disturbed at the eight-leaf stage. In the field experiment, root fragments of length 12 cm. from the same clone, were planted in October 1991 at 5 cm or 20 cm depth. Plants that developed from these fragments were studied on 12 occasions, from April to July 1992. Plants emerging from a depth of 20 cm reached a point of positive net assimilation 28 days (380 day degrees) later than those developing from a depth of 5 em. The plants exhibited a minimum regenerative capacity when their primary shoots had. on average. 10 (plants from 5-cm root fragments) or seven (plants from 20-cm root fragments) expanded leaves. 相似文献
7.
The influence of non-ionic (X-77) and organosilicone (L-77) adjuvants and of methylated seed oil (MSO) on the uptake, translocation and efficacy of glyphosate was investigated in Bidens frondosa L. and Panicum maximum Jacq. In addition, the physicochemical properties of adjuvants and adjuvant + glyphosate aqueous solutions were determined. Significantly lower surface tension and contact angle values were obtained with aqueous solutions of L-77 alone and with glyphosate. Over a 48-h time course, it was observed that >50% of applied 14 C-glyphosate was absorbed within 15 min in B. frondosa with L-77. At 6 h and thereafter, 14 C glyphosate absorption was significantly higher with MSO compared with X-77 in B. frondosa . In P. maximum , uptake and translocation of 14 C-glyphosate + adjuvant were increased in general up to 48 h after treatment application, except with L-77, which showed no improvement in uptake – instead there was a significant reduction compared with no treatment with L-77. This indicated its antagonistic effect on this grass species. The lower values of 14 C-glyphosate in P. maximum also confirmed that adjuvant effects were species specific. In the efficacy studies, glyphosate formulated with L-77 achieved significantly higher control of B. frondosa , while there was no control of P. maximum with this treatment. This confirmed antagonism in glyphosate absorption into P. maximum by L-77. Furthermore, significantly higher control of tested plants was recorded with MSO in comparison to X-77, which confirms the solubilizing or humectant nature of MSO. 相似文献
8.
Cold tolerant isolates of Gaeumannomyces graminis var. graminis ( Ggg ) and Phialophora sp. (lobed hyphopodia), which produced at least comparable growth rates at 5°C to those of pathogenic G. graminis var. tritici ( Ggt ), were shown to control take-all disease in wheat effectively in 2 years of field experiments in New South Wales, Australia. The addition of oat inoculum of these fungi at the rate of 60 kg/ha to the seeding furrow significantly ( P ≤ 0.05) reduced disease and increased grain yields by 33–45% compared to the Ggt alone treatment. The use of 30 kg/ha of oat inoculum also significantly ( P ≤ 0.05) reduced disease and increased grain yields by 21–44%. These high levels of take-all control were obtained consistently from four field experiments on three different soil types with different pHs. A treatment inoculated with Ggg alone showed no disease symptoms and produced grain yields similar to that of untreated wheat. This fungus is, therefore, non-pathogenic to wheat. At high rates of inoculation of Ggg and Phialophora sp. (lobed hyphopodia), 65–80% of tillering wheat plants (GS 32) had root systems colonized by these fungi. In contrast, two Pseudomonas spp. and an isolate each of Ggg and Phialophora sp. (lobed hyphopodia), which did not grow at 5°C, were ineffective in controlling take-all. Take-all assessments during heading (GS 61-83) were highly correlated ( R 2 =0.6047, P ≤0.0005) with the relative yield increase or decrease of inoculated treatments compared to the Ggt alone treatment. The use of a Ggg isolate (90/3B) and a Phialophora sp. (lobed hyphopodia) isolate (KY) for take-all control has been patented. These fungi are being developed for commercial use. 相似文献
9.
Two field experiments, in 1999 and 2000, were used to test whether reductions in root growth and function explained the effects of take-all on crop water and nitrogen uptake. The fungicide silthiofam was used to manipulate take-all independently of other factors. Soil water content was manipulated from heading to determine effects on disease progress and resource capture. Epidemic progress was significantly delayed in the presence of silthiofam, leading to reductions in disease in both experiments. Effects of silthiofam were reduced by increasing soil water late in the season, although only in 2000 did increased soil water content have a direct effect, leading to a higher rate of disease increase. Higher levels of disease in the absence of silthiofam did not affect root growth as measured by total root length density (TRLD), but did lead to significantly reduced healthy root length density (HRLD, a measure of functional roots) in both experiments. Only in 2000 were there any significant effects of increased take-all on water and nitrogen uptake. This was attributed to the higher TRLD in the (1999) crop, which allowed HRLDs to be maintained above a critical threshold (where water and nitrogen uptake start to be severely affected) despite loss of functional root to disease. The effects of take-all on nitrogen uptake were more likely to affect crop canopy size and duration than the relatively small effects observed on water uptake. Increasing soil water content allowed the crop to take up more water in absolute terms despite, in 2000, increasing levels of disease and reducing HRLD. 相似文献
10.
Pythium species cause necrotic lesions and root rots on tomato in soilless culture. Epidemiological studies conducted in Brittany, France, revealed the precocity and the frequency of the contamination of tomato roots by these fungi, even in symptomless roots. The colonization, estimated by culture-plate methods, could reach levels as high as 105 propagules/gram of root. The frequent occurrence of Pythium with filamentous non-inflated sporangia, representing 75% of the total isolates, was observed during both latent infections and necrotic phases. Those Pythium spp., grouped as Pythium F, induced variable necrotic lesions in tomato roots in soilless culture. This group, which had been overlooked previously in favour of known pathogenic species such as P. ultitnum var. ultimum , can be pathogenic to tomato plants and therefore form a component of a potential disease complex. 相似文献
11.
Effects of avirulent bacteriocin-producing strains of Pseudomonas solanacearum on the control of bacterial wilt of tobacco 总被引：5，自引：0，他引：5
Root systems of tobacco dipped in suspensions containing 2 × 109 colony forming units (CFU)/ml of avirulent bacteriocin-producing strains (ABPS) of Pseudomonas solanacearum and assayed immediately after planting in steam-sterilized soil had 8 × 106 CFU/root system of ABPS. The bacterial population declined to an average of 5·3 × 105 CFU/root system after 30 days. Roots of seedlings dipped in bacterial suspensions of ABPS were more effectively protected against wilt caused by P. solanacearum than those dipped in suspensions of an avirulent nonbacteriocin-producing strain (ANBPS). Lipopolysaccharide (LPS) isolated from one ABPS (121) inhibited the attachment of bacteria on roots by 70% but had no effect on the reduction of wilt, whereas bacterial cells significantly reduced the disease severity as compared to LPS or water treatment. In steam-sterilized soil containing a 1:1 mixture (5 × 105 CFU/g of oven-dried soil) of ABPS 121 or 237 and the virulent strain K-60, ABPS 121 reduced multiplication of the virulent strain in soil and in the rhizosphere of seedlings. When roots of seedlings were dipped in a suspension of 2 × 109 CFU/ml of ABPS before planting, root colonization by the virulent strain added to steam-sterilized soil at 2 × 106 CFU/g of oven-dried soil was significantly reduced. When roots were dipped in a suspension of ABPS and assayed 20 days after planting, 98% of the bacterial population was found in the original zone of inoculation and only 2% was detected in new growths of the root system. Plants which were grown in soil infested with ABPS 121 or K-60 had both strains present at variable populations along all sections of roots. 相似文献
12.
R. G. SHIVAS 《Plant pathology》1994,43(3):547-553
The effect of temperature, dew period, inoculum concentration and host maturity on the growth and development of Emex australis after inoculation with Phomopsis emicis was studied in controlled environments. Disease was assessed by recording changes in the length of stems, number of fully expanded leaves, dry weights, number of fruits and disease severity index. Disease was as severe at 18°C as it was at 28°C. There was a trend of increased disease with longer dew period. Inoculum concentrations of 1·106 and 1·107 conidia per ml resulted in a significant net reduction in stem growth compared with lower concentrations. Progressively higher disease ratings occurred as the inoculum concentration increased to 1·107 conidia per ml. There were no significant effects of inoculation with P. emicis on either seedlings, rosettes or flowering rosettes, but 10-week-old plants were highly susceptible to infection and stem collapse. The implications of these results for the potential development of P. emicis as a mycoherbicide are discussed. 相似文献
13.
K. LUND-HÖIE 《Weed Research》1969,9(3):185-191
Summary. A method of exposing seedlings of Norway spruce (Picea abies (L.) Karst.) to 14 CO2 is described. Within the 1st hr alter 14 CO2 exposure, no translocation of the 14 C out of the treated branch could be observed. After a 24-hr period, however, the 14 C in dormant seedlings had been translocated basipetally to part of the root system only, with no lateral diffusion of the 14 C-compounds in the stem. About a week after exposure, both symplastic and apoplastic patterns of translocation had caused a more uniform distribution of 14 C. In seedlings at active internode elongation, the translocation patterns were fundamentally identical to those in dormant seedlings, but the active shoot growth had led to a more uniform distribution of the 14 C.
Simazine at 20 ppm had apparently stimulated both the photofixation of14 CO2 and the rate of translocation of the 14 C-assimilates. At 30 ppm, however, simazine had blocked the translocation of nutrients to the roots. On the other hand, the 14 CO2 uptake was not influenced. The simazine incubation had apparently no influence on the synthesis of cationic photosynthate. 相似文献
Simazine at 20 ppm had apparently stimulated both the photofixation of
14.
Effect of temperature on latent period of septoria leaf blotch on winter wheat under outdoor conditions 总被引：1，自引：0，他引：1
D. J. Lovell † T. Hunter S. J. Powers S. R. Parker ‡ F. Van den Bosch 《Plant pathology》2004,53(2):170-181
Batches of two winter wheat cultivars (Riband and Apollo) were inoculated with conidia of Mycosphaerella graminicola at weekly intervals over a 2 year period. Following 72 h incubation, plants were placed in ambient temperatures ranging between −7 and 32°C with mean batch temperatures of 2·9–20·2°C. Latent period until the first visible symptoms ranged between 11 and 42 days. The relationship between development of lesions and accumulated thermal time was described using a shifted cumulative gamma distribution model. The model provided good estimates of lesion development with r 2 > 0·92 for both cultivars. Base temperatures, below which the pathogen did not develop, were estimated from the model as approximately −2·4°C for the two cultivars. Latent period was estimated as being 250 and 301 degree-days above the estimated base temperature, when defined as time from inoculation to first lesion and time to 50% of maximal lesions, respectively, for cv. Riband. The values for cv. Apollo were similar, but with estimates of thermal time periods c . 5% higher. The relationship between mean temperature and inverse latent period, expressed as days either to first lesion or to 50% of maximal lesions, was best described by a linear regression with r 2 > 0·96 for both cultivars. The opportunity for plants to outgrow disease was reduced when prolonged periods of cold temperature occurred, because the base temperature for growth of the pathogen was less than that for the crop. 相似文献
15.
First leaves of barley seedlings grown in solution culture were inoculated with powdery mildew when the second leaf was fully emerged. 14 C-labelled carbon dioxide was fed to either first or second leaves of infected and non-infected plants. Translocation of labelled photoassimilates into roots, and partitioning into soluble, storage and structural fractions were studied in tip, mid and basal regions of primary roots 24 h after feeding. Mildew reduced the total activity in the plant, but had little effect on assimilate distribution since the percentage activity translocated to roots was only transiently reduced, approximately 7 days after infection. Reduced import led to a reduction in the specific activity of different fractions within roots, reductions being greatest in root tips. These changes were similar whichever leaf was fed. Changes in specific activity became progressively more pronounced in the 10 days following infection, and were paralleled by a reduction in the mitotic index of root tips. It is concluded that meristematic activity, and thus the growth, of primary roots of barley is particularly sensitive to reductions in photoassimilation caused by powdery mildew infection. 相似文献
16.
R. N. Graça A. C. Alfenas L. A. Maffia M. Titon R. F. Alfenas D. Lau J. M. A. Rocabado 《Plant pathology》2009,58(5):971-981
The pattern of Cylindrocladium pteridis adhesion, germination and penetration in eucalypt leaves was assessed using scanning electron microscopy. The effects of inoculum concentration, leaf wetness period, plant age and branch position of cylindrocladium leaf blight and defoliation severity were assessed in greenhouse studies using two Eucalyptus grandis × E. urophylla hybrid clones. Penetration occurred through stomata, and there was no difference in the number of penetrations between young and old leaves. Percentage leaf area with lesions and defoliation increased with the increase in inoculum concentration (1 × 102 to 105 conidia mL−1 ), duration of leaf wetness period (6 to 48 h) and plant age (60 to 180 days). Branch position in plants also significantly affected the percentage leaf area with lesions and defoliation, the latter variable being significantly higher at the stem base. The highest values of lesion area were also observed on leaves at the stem base in both clones. The Pearson correlation between defoliation and leaf area with lesions was significant in all experiments ( r > 0·9) indicating a high association between these two variables. 相似文献
17.
More than 20000 wheat plants, derived from callus culture of immature wheat embryos were assessed for reaction to the take-all fungus ( Gaeumannomyces graminis var. tritici ) using a test-tube assay. Lines with less root and shoot blackening and more remaining green tissue than parental lines were identified in the SC3 generation. However these lines had more root and shoot blackening and less remaining green tissue in subsequent generations. The changes in reaction to the fungus may therefore have been epigenetic. The potential of this tissue culture derived material for breeding take-all resistant wheats is discussed. 相似文献
18.
ABSTRACT Wheat was assessed at four crop growth stages for take-all (Gaeumannomyces graminis var. tritici) in a series of field trials that studied the effects of five wheat management practices: sowing date, plant density, nitrogen fertilizer dose and form, and removal/burial of cereal straw. An equation expressing disease level as a function of degree days was fitted to the observed disease levels. This equation was based on take-all epidemiology and depended on two parameters reflecting the importance of the primary and secondary infection cycles, respectively. Early sowing always increased disease frequency via primary infection cycle; its influence on the secondary cycle was variable. Primary infection and earliness of disease onset were increased by high density; however, at mid-season take-all was positively correlated to the root number per plant, which was itself negatively correlated to plant density. At late stages of development, neither plant density nor root number per plant had any influence on disease. A high nitrogen dose increased both take-all on seminal roots and severity of primary infection cycle but decreased take-all on nodal roots and secondary infection cycle. Ammonium (versus ammonium nitrate) fertilizer always decreased disease levels and infection cycles, whereas straw treatment (burial versus removal of straw from the previous cereal crop) had no influence. 相似文献
19.
Point pattern analysis (fitting of the beta-binomial distribution and binary form of power law) was used to describe the spatial pattern of natural take-all epidemics (caused by Gaeumannomyces graminis var. tritici ) on a second consecutive crop of winter wheat in plots under different cropping practices that could have an impact on the quantity and spatial distribution of primary inoculum, and on the spread of the disease. The spatial pattern of take-all was aggregated in 48% of the datasets when disease incidence was assessed at the plant level and in 83% when it was assessed at the root level. Clusters of diseased roots were in general less than 1 m in diameter for crown roots and 1–1·5 m for seminal roots; when present, clusters of diseased plants were 2–2·5 m in diameter. Anisotropy of the spatial pattern was detected and could be linked to soil cultivation. Clusters did not increase in size over the cropping season, but increased spatial heterogeneity of the disease level was observed, corresponding to local disease amplification within clusters. The relative influences of autonomous spread and inoculum dispersal on the size and shape of clusters are discussed. 相似文献
20.
Zahida Iqbal Syuntaro Hiradate Akio Noda Sei-Ichi Isojima Yoshiharu Fujii 《Weed Biology and Management》2002,2(2):110-115
The allelopathic potential of buckwheat ( Fagopyrum esculentum ) was investigated. Field study showed that living buckwheat reduced weed biomass compared with plots without buckwheat. Laboratory study revealed that root exudates suppressed root and shoot growth of weeds and reduced weed dry weight. Sequential partitioning of the aqueous ethanolic extract of the aerial parts of buckwheat showed that the chloroform extract caused an 80% reduction in radicle elongation of lettuce seedlings at a concentration of less than 100 p.p.m. Fagomine, 4-piperidone and 2-piperidinemethanol were isolated and identified by 1 H and 13 C nuclear magnetic resonance from the chloroform extract. These compounds caused a 50% inhibition of radicle elongation in lettuce seedlings at concentrations of less than 100 p.p.m. These results suggest that compounds 1, 2, and 3 might act as allelochemicals and affect the growth or germination of different plant species. 相似文献